The demand for small-sized computing devices is continuously increasing. Computing device in this context refers to an apparatus that comprises computer hardware and software required to perform predefined series of arithmetic or logical operations.
For example, in mobile communications the tendency has continuously been towards smaller terminal units. The need for an appropriate match between the size of human fingers and the size of the input keys has, however, by far dictated the dimensioning of the mobile stations. People have generally considered it more important to be able to input keystrokes conventionally with their fingers, even if it means that the device is then bigger and needs to be carried separately in a pocket, a separate supporter or a purse. Smaller size terminals would in many cases be practical but so far it has not been possible to implement very small devices without compromising the comfortable look and feel of the user interface of conventional terminals.
Other examples of carefully dimensioned computing devices are wearable computers, i.e. computers worn on the body. Wearable computers have been considered especially useful for applications where computational support or monitoring is provided continuously, even when the user's hands, voice, eyes or attention are most of the time actively engaged with other things, like the physical environment. In case of wearable devices the dimension is naturally of utmost importance. The wearable device must be easily reached for input and output operations, but it must not interfere with the actions performed by the user. If, for example, the wearable device is strapped to the wrist, it must not protrude too far from the wrist to complicate dressing or arm movements of the user.
In some computing devices the dimensioning problem has been solved by combining input and output operations to touch screens. However, in many cases users experience that the finger is too clumsy to operate the screen and they do not wish to carry a stylus for operating the touch screen of the otherwise fully wearable device. For some users and in some environments very precise hand motions are not even possible. Many times the operating finger also blocks visibility to the information displayed in the screen, which makes comfortable interaction with menu selections practically impossible. For example, in a computing device that is strapped to the wrist the screen is typically a circle of 3-4 cm diameter. Using this size of screen simultaneously for both input and output operations is in most of the wearable computer applications not viable.
In some other small-sized computing devices the dimensioning problem has been solved by replacing the keys with a input wheel. The computing device receives commands by interpreting movements of the finger on the wheel and runs through a predefined group of menu options according to these movements. A choice of an option is confirmed by pressing a tactile button within the wheel. The wheel is separate from the screen such that the visibility of the screen remains good at all times. Also the use of circular movements has been considered very intuitive and pleasant in operation. However, the separation results in that the size of the computing device is the combined size of the screen and the wheel. For a very small device, like a wrist computer, this is already too much.
In traditional wrist computers the display screen is mounted in a frame that may comprise a number of tactile keys. The input operations are then given by means of a single keystroke or a combination of keystrokes. However, these buttons are typically relatively small and for many users, like elderly people or infants, the size and tactile feeling of such buttons does not provide appropriate response and their use is considered too complicated. Also in many conditions, like in outdoor environment, production lines, or rescue operations the protective clothing used in hands prevents efficient operations of small-sized buttons. Furthermore, the placing of such buttons becomes especially difficult when shielding distances to an integrated antenna need to be considered.
Accordingly, dimensioning of the input/output operations to a compact computing device is challenging as such. However, when the computing device also needs to provide a wireless communication interface to an external node, the design gets even more complicated. Wireless access requires use of antenna that needs to operate in an acceptable level. Typically operations of the antenna are protected by not placing any strongly dielectric materials close to the antenna. In design, the shielding distance corresponds to a distance where a dielectric object brought into the vicinity of the antenna begins to disturb normal operations of the radio unit. Any dielectric materials, including circuitry for detecting user inputs, need to be appropriately distanced from the antenna. Therefore computing devices with an easy-to-use user interface and a radio unit very often end up in relatively massive configurations.